Information processing device

ABSTRACT

A reinforcement information adjustment unit reduces an amount of information in reinforcement information by combining: update cycle adjustment processing to set an update cycle of the reinforcement information to be an integer multiple of a predetermined update cycle; geographic interval error value adjustment processing to reduce the number of geographic interval error values by selecting from among a plurality of the geographic interval error values each of which is an error at every predetermined geographic interval out of a plurality of error values, a geographic interval error value at every geographic interval that is an integer multiple of the predetermined geographic interval; and bit count adjustment processing to reduce a bit count of the error value for each error value. A reinforcement information output unit outputs, to an output destination, reinforcement information after being reduced in the amount of information by the reinforcement information adjustment unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityfrom U.S. application Ser. No. 15/518,497, filed on Apr. 12, 2017, whichclaims the benefit of prior International Application No.PCT/JP2015/080657 filed on Oct. 30, 2015, which is based upon and claimsthe benefit of priority from Japanese Patent Application No. 2014-221755filed on Oct. 30, 2014; the entire contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to satellite positioning.

BACKGROUND ART

In an independent positioning scheme in which a positioning deviceindependently determines a position by using code information of a GNSSsignal from a satellite positioning system (GNSS: Global NavigationSystem) such as a GPS (Global Positioning System), an error included inthe GNSS signal results in positioning accuracy on the order of meters.

Compared to the independent positioning scheme, a positioning schemeusing reinforcement information realizes high accuracy positioning onthe order of centimeters.

This positioning scheme uses observed data at an electronic referencepoint or the like, the accurate coordinates of which are known, toestimate an error arising from a positioning satellite and an errorarising from an atmospheric state for each positioning satellite andprovide an amount of error correction as the reinforcement informationto a positioning device.

The reinforcement information is transmitted from a quasi-zenithsatellite or a wireless LAN (Local Area Network) network, for example,to be provided to the positioning device.

The positioning device performs error correction on a result ofindependent positioning by using the amount of error correction in thereinforcement information to thus be able to realize high accuracypositioning on the order of centimeters.

A technique disclosed in Patent Literature 1 relates to the highaccuracy positioning using the reinforcement information, for example.

CITATION LIST Patent Literature

Patent Literature 1: JP 2014-16315 A

SUMMARY OF INVENTION Technical Problem

It is desired to use reinforcement information on the order ofcentimeters in order to realize satellite positioning with highaccuracy.

On the other hand, a communication bandwidth of as much as 2 Kbps (bitsper second) is required to transmit the reinforcement information on theorder of centimeters.

The quasi-zenith satellite or the wireless LAN network transmitsinformation used in various services in addition to the reinforcementinformation, where there is a problem that transmission of thereinforcement information constrains a communication bandwidth used foranother information.

It is one of the main objects of the present invention to solve theaforementioned problem, and it is the main object to achieve highaccuracy positioning without constraining the communication bandwidth.

Solution to Problem

An information processing device according to the present invention mayinclude:

a reinforcement information adjustment unit to reduce an amount ofinformation in reinforcement information that is updated in apredetermined update cycle, includes a plurality of error values, and isused to correct a satellite positioning error; and

a reinforcement information output unit to output, to an outputdestination, the reinforcement information after being reduced in theamount of information by the reinforcement information adjustment unit,wherein

the reinforcement information adjustment unit reduces the amount ofinformation in the reinforcement information by combining:

update cycle adjustment processing to set an update cycle of thereinforcement information to be an integer multiple being twice or moreof the predetermined update cycle;

geographic interval error value adjustment processing to reduce thenumber of geographic interval error values by selecting from among aplurality of the geographic interval error values each of which is anerror at every predetermined geographic interval in a plurality of gridpoints, out of the plurality of error values, a geographic intervalerror value at every geographic interval that is an integer multiplebeing twice or more of the predetermined geographic interval in each ofa latitude direction and a longitude direction; and

bit count adjustment processing to reduce a bit count of the errorvalue, for each error value relevant to a carrier wave, starting from aleast significant bit, such that a bit count after reduction is smallerthan a bit count before the reduction.

Advantageous Effects of Invention

According to the present invention, the communication bandwidth can beused effectively by reducing an amount of information in reinforcementinformation.

Moreover, according to the present invention, the reinforcementinformation is manipulated to realize high accuracy positioning so thatrelatively high positioning accuracy can be maintained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration example of apositioning system according to a first embodiment.

FIG. 2 is a diagram illustrating a grid point according to the firstembodiment.

FIG. 3 is a diagram illustrating a configuration example of aninformation processing device according to the first embodiment.

FIG. 4 is a flowchart illustrating an operational example of theinformation processing device according to the first embodiment.

FIG. 5 is a flowchart illustrating an example of processing thatgenerates reinforcement information on the order of decimeters,according to the first embodiment.

FIG. 6 is a diagram illustrating an example of update cycle adjustmentprocessing according to the first embodiment.

FIG. 7 is a diagram illustrating an example of geographic interval errorvalue adjustment processing according to the first embodiment.

FIG. 8 is a diagram illustrating an example of bit count adjustmentprocessing according to the first embodiment.

FIG. 9 is a diagram illustrating an example of geographic interval errorvalue adjustment processing according to a second embodiment.

FIG. 10 is a diagram illustrating a configuration example of apositioning device according to a third embodiment.

FIG. 11 is a table illustrating components of the positioning deviceaccording to the third embodiment.

FIG. 12 is a table illustrating intermediate data of the positioningdevice according to the third embodiment.

FIG. 13 is a table illustrating an example of a threshold tableaccording to the third embodiment.

FIG. 14 is a diagram illustrating a processing flow of a Kalman filteraccording to the third embodiment.

FIG. 15 is a table illustrating a vector and a matrix used in the Kalmanfilter according to the third embodiment.

FIG. 16 is a diagram illustrating an operational example of a processnoise adjustment unit according to the third embodiment.

FIG. 17 is a diagram illustrating an operational example of anobservation noise calculation unit according to the third embodiment.

FIG. 18 is a diagram illustrating an operational example of anobservation update calculation unit according to a fourth embodiment.

FIG. 19 is a diagram illustrating an example of a hardware configurationof the information processing device and the positioning deviceaccording to the first to fourth embodiments.

DESCRIPTION OF EMBODIMENTS First Embodiment

***Description of Configuration***

FIG. 1 is a diagram illustrating a configuration example of apositioning system according to the present embodiment.

An information processing device 100 in FIG. 1 generates reinforcementinformation on the order of centimeters and degrades the generatedreinforcement information on the order of centimeters to generatereinforcement information on the order of decimeters.

The information processing device 100 then provides the reinforcementinformation on the order of decimeters to a quasi-zenith satellite 200or a wireless LAN network 800 to be described.

Note that the reinforcement information on the order of centimeters is apiece of information used to correct a positioning error that occurs inindependent positioning using a positioning signal from a GPS satellite,and is a piece of reinforcement information by which positioningaccuracy on the order of centimeters is achieved as positioning accuracyafter the correction.

The positioning accuracy on the order of centimeters means that thepositioning error falls within the order of two to three centimeterswith a probability of 65% or higher.

On the other hand, the reinforcement information on the order ofdecimeters is a piece of information used to correct the positioningerror that occurs in independent positioning using the positioningsignal from the GPS satellite, and is a piece of reinforcementinformation by which positioning accuracy on the order of decimeters isachieved as the positioning accuracy after the correction.

The positioning accuracy on the order of decimeters means that thepositioning error falls within the order of 20 to 30 centimeters with aprobability of 65% or higher.

The quasi-zenith satellite 200 receives reinforcement information on theorder of decimeters 400 obtained by the information processing device100 from a transmitter 700, and transmits the reinforcement informationon the order of decimeters being received to the earth.

The quasi-zenith satellite 200 transmits the reinforcement informationon the order of decimeters 400 with any one of frequencies L1, L2, andL5, for example.

Note that while the present embodiment describes an example oftransmitting the reinforcement information on the order of decimeters400 from the quasi-zenith satellite 200, the reinforcement informationon the order of decimeters 400 may instead be transmitted from asatellite other than the quasi-zenith satellite 200. Alternatively, thereinforcement information on the order of decimeters 400 may betransmitted from the wireless LAN network 800 providing a wireless LANenvironment.

A GPS satellite 300 being a positioning satellite transmits apositioning signal 500.

A GNSS satellite such as GLONASS, Galileo, or BeiDou may be used insteadof the GPS satellite 300.

Moreover, the GPS satellite 300 may be adapted to transmit thereinforcement information on the order of decimeters 400.

The positioning signal 500 includes observed data 501 and a broadcastephemeris 502.

A pseudorange between a positioning point and the GPS satellite 300 aswell as a carrier phase can be derived from the observed data 501.

Each of the pseudorange and the carrier phase derived from the observeddata 501 includes an error.

A positioning device 600 uses the reinforcement information on the orderof decimeters 400 to eliminate the error included in each of thepseudorange and the carrier phase.

The broadcast ephemeris 502 is a piece of data notifying of an accuratesatellite orbit of the GPS satellite 300 from which the broadcastephemeris 502 is transmitted, and is also called an ephemeris.

The positioning device 600 can be a smart phone, a mobile phone, atablet terminal, or a car navigation system, for example.

The positioning device 600 receives the positioning signal 500transmitted from the GPS satellite 300.

The positioning device 600 also receives the reinforcement informationon the order of decimeters 400 transmitted from the quasi-zenithsatellite 200 or the wireless LAN network 800.

When receiving the reinforcement information on the order of decimeters400 from the quasi-zenith satellite 200, the positioning device 600needs to support any one of the frequencies L1, L2, and L5.

The positioning device 600 applies the reinforcement information on theorder of decimeters 400 to the positioning signal 500 (including apositioning error on the order of meters) to be able to obtain apositioning result with positioning accuracy on the order of decimeters.

The transmitter 700 transmits the reinforcement information on the orderof decimeters 400 generated by the information processing device 100 tothe quasi-zenith satellite 200.

Now, there will be described an error value included in thereinforcement information on the order of centimeters.

The reinforcement information on the order of centimeters includes avalue of a satellite clock error (hereinafter simply referred to as asatellite clock error), a value of a satellite orbit error (hereinaftersimply referred to as a satellite orbit error), an inter-frequency bias,a value of an ionospheric delay error (hereinafter simply referred to asan ionospheric delay error), and a value of a tropospheric delay error(hereinafter simply referred to as a tropospheric delay error).

The satellite clock error, the satellite orbit error, and theinter-frequency bias are errors independent of a region.

The ionospheric delay error and the tropospheric delay error are errorsdependent on a region and are calculated for each grid point.

The grid point is a virtual measurement point arranged at approximately60-km intervals in each of a latitude direction and a longitudedirection as illustrated in FIG. 2.

The ionospheric delay error and the tropospheric delay error correspondto a geographic interval error value to be described later.

Note that the reinforcement information on the order of centimeters isupdated in a predetermined update cycle (specifically, the satelliteclock error is updated in a cycle of five seconds, while the othererrors being the satellite orbit error, the inter-frequency bias, theionospheric delay error and the tropospheric delay error are updated ina cycle of 30 seconds).

FIG. 3 is a diagram illustrating a configuration example of theinformation processing device 100 according to the present embodiment.

A reinforcement information generation unit 101 in FIG. 3 generates thereinforcement information on the order of centimeters.

The reinforcement information generation unit 101 may generate thereinforcement information on the order of centimeters by an arbitrarymethod.

A reinforcement information adjustment unit 102 reduces the amount ofinformation in the reinforcement information on the order of centimetersgenerated by the reinforcement information generation unit 101 togenerate the reinforcement information on the order of decimeters.

More specifically, the reinforcement information adjustment unit 102reduces the amount of information in the reinforcement information onthe order of centimeters by combining update cycle adjustment processing1021, geographic interval error value adjustment processing 1022, andbit count adjustment processing 1023.

The update cycle adjustment processing 1021 is processing that sets theupdate cycle of the reinforcement information on the order ofcentimeters to be an integer multiple of the predetermined update cycle.

In the present embodiment, as an example of the update cycle adjustmentprocessing 1021, there will be described processing that sets the updatecycle of the reinforcement information on the order of centimeters to acycle of 60 seconds being twice the original cycle of 30 seconds. Notethat in the update cycle adjustment processing 1021, the update cycle ofthe reinforcement information on the order of centimeters may beadjusted to an integer multiple being twice or larger of the originalupdate cycle, not necessarily twice.

The geographic interval error value adjustment processing 1022 isprocessing that reduces the number of geographic interval error valuesby selecting the geographic interval error value every geographicinterval being an integer multiple of a predetermined geographicinterval from among a plurality of geographic interval error values thatis an error in the every predetermined geographic interval.

In the present embodiment, as an example of the geographic intervalerror value adjustment processing 1022, there will be describedprocessing that reduces the number of each of the ionospheric delayerrors and the tropospheric delay errors by extracting the ionosphericdelay error and the tropospheric delay error every 180 km being threetimes as long as 60 km that is the grid point interval in each of thelatitude direction and the longitude direction. Note that in thegeographic interval error value adjustment processing 1022, theionospheric delay error and the tropospheric delay error may beextracted every geographic interval being an integer multiple beingtwice or larger of the original grid point interval, not necessarilythree times.

The bit count adjustment processing 1023 is processing that reduces abit count of the error value for each error value.

In the present embodiment, as an example of the bit count adjustmentprocessing 1023, there will be described processing that reduces the bitcount, for each error value relevant to the carrier wave, starting fromthe least significant bit, such that the bit count after reduction isequal to any bit count between 60% and 80% of the bit count before thereduction. Note that in the bit count adjustment processing 1023, thebit count may be reduced starting from the least significant bit suchthat the bit count after the reduction is smaller than the bit countbefore the reduction, not necessarily equal to the bit count between 60%and 80% of the bit count before the reduction.

A reinforcement information output unit 103 outputs, to an outputdestination, the reinforcement information on the order of decimetersbeing the reinforcement information after the amount of information isreduced.

The output destination of the reinforcement information output unit 103is an interface of the transmitter 700 or an interface of the wirelessLAN network 800, for example.

***Description of Operation***

Next, an operational example of the information processing device 100according to the present embodiment will be described.

FIG. 4 is a flowchart illustrating an operational example of theinformation processing device 100 according to the present embodiment.

First, in step S101, the reinforcement information generation unit 101generates the reinforcement information on the order of centimeters.

Then in step S102, the reinforcement information adjustment unit 102degrades the reinforcement information on the order of centimeters togenerate the reinforcement information on the order of decimeters.

Finally, in step S103, the reinforcement information output unit 103outputs the reinforcement information on the order of decimetersgenerated by the reinforcement information adjustment unit 102 to theoutput destination.

The output destination of the reinforcement information output unit 103is the interface of the transmitter 700 or the interface of the wirelessLAN network 800 as described above, for example.

Next, there will be described in detail the operation in step S102illustrated in FIG. 4.

FIG. 5 is a flowchart illustrating the details of S102.

First, in S1021, the reinforcement information adjustment unit 102performs the update cycle adjustment processing.

The update cycle adjustment processing will be described in detail withreference to FIG. 6.

A data stream of the reinforcement information on the order ofcentimeters is illustrated in (a) of FIG. 6.

As illustrated in (a) of FIG. 6, the update cycle of the reinforcementinformation on the order of centimeters is 30 seconds.

Reinforcement information (t=0) is the reinforcement information on theorder of centimeters transmitted from the quasi-zenith satellite 200 orthe wireless LAN network 800 between time t=0 and time t=30.

Reinforcement information (t=30) is the reinforcement information on theorder of centimeters transmitted from the quasi-zenith satellite 200 orthe wireless LAN network 800 between time t=30 and time t=60.

The same applies to time t=60 onward.

During 30 seconds from time t=0 to time t=30, the satellite clock error,the satellite orbit error, the inter-frequency bias, the ionosphericdelay error at each grid point, and the tropospheric delay error at eachgrid point at a measurement timing T0 (T0<(t=0)) are transmitted as thereinforcement information (t=0).

Then, during 30 seconds from time t=30 to time t=60, the satellite clockerror, the satellite orbit error, the inter-frequency bias, theionospheric delay error at each grid point, and the tropospheric delayerror at each grid point at a new measurement timing T1 (T1<(t=30)) aretransmitted as the reinforcement information (t=30).

The same applies to time t=60 onward.

Note that, strictly speaking, the satellite clock error is transmittedfive times during 30 seconds since a satellite clock error is updatedevery five seconds, but the reinforcement information as a whole isupdated in the cycle of 30 seconds.

As illustrated in (a) of FIG. 6, the reinforcement informationgeneration unit 101 repeatedly generates the reinforcement informationon the order of centimeters in increments of 30 seconds and inputs theinformation to the reinforcement information adjustment unit 102.

As illustrated in (b) of FIG. 6, the reinforcement informationadjustment unit 102 selects the reinforcement information on the orderof centimeters in increments of 60 seconds.

In an example illustrated in (b) of FIG. 6, the reinforcementinformation adjustment unit 102 selects the reinforcement information(t=0) between time t=0 and time t=30, and spends 60 seconds transmittingthe reinforcement information (t=0).

That is, the reinforcement information adjustment unit 102 transmits thereinforcement information (t=0) at a rate half the transmission rate in(a) of FIG. 6.

The reinforcement information adjustment unit 102 does not select thefollowing reinforcement information (t=30) between time t=30 and timet=60.

Moreover, the reinforcement information adjustment unit 102 selects thereinforcement information (t=60) between time t=60 and time t=90, andspends 60 seconds transmitting the reinforcement information (t=60).

That is, the reinforcement information adjustment unit 102 transmits thereinforcement information (t=60) at a rate half the transmission rate in(a) of FIG. 6.

The reinforcement information adjustment unit 102 does not select thefollowing reinforcement information (t=90) between time t=90 and timet=120.

Only the reinforcement information on the order of centimeters selectedin the update cycle adjustment processing (S1021) is subjected to theprocessing from S1022 onward.

The number of pieces of reinforcement information on the order ofcentimeters to be subjected to the processing in S1022 is reduced byhalf when the update cycle adjustment processing (S1021) is performed bythe method illustrated in (b) of FIG. 6.

Referring back to FIG. 5, the reinforcement information adjustment unit102 performs the geographic interval error value adjustment processingin S1022.

The reinforcement information adjustment unit 102 performs thegeographic interval error value adjustment processing on eachreinforcement information on the order of centimeters selected in S1021.

The geographic interval error value adjustment processing will bedescribed in detail with reference to FIG. 7.

Each point in FIG. 7 indicates the grid point.

The reinforcement information on the order of centimeters selected inS1021 each includes the ionospheric delay error and the troposphericdelay error of all the grid points.

In S1022, the reinforcement information adjustment unit 102 reduces thenumber of each of the ionospheric delay errors and the troposphericdelay errors by selecting the ionospheric delay error and thetropospheric delay error every three grid points (180 km) in each of thelatitude direction and the longitude direction from among theionospheric delay errors and the tropospheric delay errors of all thegrid points included in the reinforcement information on the order ofcentimeters.

As a result of the reduction, only the ionospheric delay error and thetropospheric delay error corresponding to the grid point filled in withblack in FIG. 7 are selected to be subjected to the processing in S1023.

The number of each of the ionospheric delay errors and the troposphericdelay errors to be subjected to the processing in S1023 is reduced toone ninth when the geographic interval error value adjustment processing(S1022) is performed by the method illustrated in FIG. 7.

That is, a multiplication of one third in the latitude direction by onethird in the longitude direction gives one ninth overall.

Note that a reference numeral 701 and a reference numeral 702 in FIG. 7indicate the ionospheric delay error and the tropospheric delay errorincluded in the reinforcement information on the order of centimeters.

The positioning device 600 can calculate estimated values (a referencenumeral 703 and a reference numeral 704) of the ionospheric delay errorand the tropospheric delay error at a grid point not included in thereinforcement information on the order of centimeters by performinglinear interpolation between the ionospheric delay errors and thetropospheric delay errors (the reference numeral 701 and the referencenumeral 702) included in the reinforcement information on the order ofcentimeters.

However, actual ionospheric delay error and tropospheric delay error canpossibly have errors (a reference numeral 705 and a reference numeral706) with respect to the estimated values (the reference numeral 703 andthe reference numeral 704).

The reinforcement information adjustment unit 102 notifies of a decreasein reliability caused by the errors (the reference numeral 705 and thereference numeral 706) with respect to the estimated values at the gridpoint not included in the reinforcement information on the order ofcentimeters in the form of integrity information to be described later.

Referring back to FIG. 5, the reinforcement information adjustment unit102 performs the bit count adjustment processing in S1023.

The bit count adjustment processing will be described in detail withreference to FIG. 8.

In FIG. 8, a reference numeral 801 denotes an error value on the orderof centimeters and a reference numeral 802 denotes an error value on theorder of decimeters.

The error value on the order of centimeters 801 is each error valueincluded in the reinforcement information on the order of centimeters.

The error value on the order of decimeters 802 is an error valueobtained after reducing the bit count of the error value on the order ofcentimeters 801.

In the bit count adjustment processing (S1023), the reinforcementinformation adjustment unit 102 reduces the bit count, for each errorvalue relevant to the carrier wave, starting from the least significantbit (LSB), such that the bit count of the error value on the order ofdecimeters 802 is equal to any bit count between 60% and 80% of the bitcount of the error value on the order of centimeters 801.

When the error value on the order of centimeters 801 has 20 bits, forexample, the reinforcement information adjustment unit 102 reduces thebit count such that the bit count of the error value on the order ofdecimeters 802 is equal to any value between 12 bits and 16 bits.

The reinforcement information adjustment unit 102 reduces the satelliteclock error, the satellite orbit error, and the inter-frequency biasincluded in the reinforcement information on the order of centimetersselected in S1021 and the bit count of each of the ionospheric delayerror and the tropospheric delay error (the ionospheric delay error andthe tropospheric delay error corresponding to the grid point filled inwith black in FIG. 7) included in the reinforcement information on theorder of centimeters and selected in S1022.

Note that the reinforcement information adjustment unit 102 notifies ofthe decrease in reliability caused by reducing the bit count in the formof the integrity information to be described later.

Through S1021 to S1023 described above, the amount of information in thereinforcement information on the order of centimeters is reduced to bethe reinforcement information on the order of decimeters.

A bandwidth of 2 Kbps is required to transmit the reinforcementinformation on the order of centimeters, while a bandwidth at a level of250 bps is sufficient to transmit the reinforcement information on theorder of decimeters.

As a result, the data volume can be reduced to approximately one eighthby converting the reinforcement information on the order of centimetersinto the reinforcement information on the order of decimeters.

Moreover, the reinforcement information adjustment unit 102 uses thereduced bit count and information on the reduced grid point to be ableto calculate reliability of the reinforcement information when theamount of information therein is reduced, on the basis of reliability ofthe reinforcement information obtained from the reinforcementinformation on the order of centimeters.

The reinforcement information adjustment unit 102 can find thereliability of the reinforcement information on the order of decimetersby obtaining a root sum square (RSS) of the reliability of thereinforcement information on the order of centimeters, the decrease inthe reliability caused by the bit reduction, and the decrease in thereliability caused by reducing the grid point.

That is, the reinforcement information adjustment unit 102 calculates aroot sum square RSS of the error 705 and the error 706 illustrated inFIG. 7 and calculates a root sum square RSS of an error corresponding tothe bit count reduced as illustrated in FIG. 8 to find the reliabilityof the reinforcement information on the order of decimeters.

The reinforcement information adjustment unit 102 then includes thereliability as the integrity information into the reinforcementinformation.

The reinforcement information adjustment unit 102 thus generates theintegrity information notifying of the decrease in reliability of thepositioning accuracy caused by the geographic interval error valueadjustment processing and the bit count adjustment processing andincludes the integrity information being generated into thereinforcement information on the order of decimeters.

The reinforcement information output unit 103 transmits thereinforcement information including the integrity information.

The integrity information allows a user who uses the reinforcementinformation on the order of decimeters to find reliability of ameasurement result from the basis of the reinforcement information inreal time and is an essential piece of information in controlling amoving body.

***Description of Effect***

According to the present embodiment described above, the reinforcementinformation on the order of centimeters is converted to thereinforcement information on the order of decimeters to be able tocompress the data volume of the reinforcement information down toapproximately one eighth and allow the communication bandwidth to beused effectively.

Moreover, as the reinforcement information on the order of centimetersrequires 2 Kbps to be transmitted, an L6 frequency needs to be used whenthe information is transmitted from the quasi-zenith satellite or thelike.

The reinforcement information on the order of decimeters can betransmitted at the level of 250 bps so that the L1, L2, or L5 frequencycan be used when the information is transmitted from the quasi-zenithsatellite or the like.

The smart phone, mobile phone, tablet terminal, and car navigationsystem generally support the L1, L2, or L5 frequency and can thusrealize positioning with relatively high accuracy on the order ofdecimeters even without a circuit or the like for the L6 frequency.

Second Embodiment

There has been described the method of reducing the number of each ofthe ionospheric delay errors and the tropospheric delay errors in thefirst embodiment.

In the present embodiment, there will be described a method ofgenerating reinforcement information on the order of decimeters withoutreducing the number of each of the ionospheric delay errors and thetropospheric delay errors.

***Description of Configuration***

In the present embodiment as well, a positioning system has an overallconfiguration as illustrated in FIG. 1, and an information processingdevice 100 has an internal configuration as illustrated in FIG. 3.

Note, however, that an operation of a reinforcement informationadjustment unit 102 differs in the present embodiment.

As geographic interval error value adjustment processing 1022, thereinforcement information adjustment unit 102 of the present embodimentanalyzes a plurality of geographic interval error values, calculates acoefficient value of a coefficient included in an approximate expressionused to calculate an approximate value of the geographic interval errorvalue for each geographic interval, and includes the coefficient valuefor each geographic interval into reinforcement information in place ofthe plurality of geographic interval error values.

That is, the reinforcement information adjustment unit 102 analyzes aplurality of ionospheric delay errors included in reinforcementinformation on the order of centimeters that is selected in S1021 ofFIG. 5 and calculates, for each grid point, a coefficient value of acoefficient included in an approximate expression used to calculate anapproximate value of the ionospheric delay error at each grid point. Thereinforcement information adjustment unit 102 further analyzes aplurality of tropospheric delay errors included in the reinforcementinformation on the order of centimeters that is selected in S1021 andcalculates, for each grid point, a coefficient value of a coefficientincluded in an approximate expression used to calculate an approximatevalue of the tropospheric delay error at each grid point.

The reinforcement information adjustment unit 102 then includes, inplace of the ionospheric delay error, the calculated coefficient valuefor each grid point into the reinforcement information on the order ofcentimeters that is selected in S1021.

Moreover, the reinforcement information adjustment unit 102 includes, inplace of the tropospheric delay error, the calculated coefficient valuefor each grid point into the reinforcement information on the order ofcentimeters that is selected in S1021.

Note that in the present embodiment, what is different from the firstembodiment will mainly be described.

Matters not described below are to the same as those of the firstembodiment.

***Description of Operation***

In the present embodiment as well, an operation of the informationprocessing device 100 is as illustrated in FIGS. 4 and 5 except for apoint described below.

Processing in S1022 in FIG. 5 is different in the present embodiment.

The operation of the reinforcement information adjustment unit 102according to the present embodiment will be described with reference toFIG. 5.

Processing in S1021 of FIG. 5 is the same as that of the firstembodiment.

That is, as illustrated in FIG. 6, the reinforcement informationadjustment unit 102 selects the reinforcement information on the orderof centimeters to be subjected to the processing in S1022 from amongpieces of reinforcement information on the order of centimeters inputfrom a reinforcement information generation unit 101.

In S1022, the reinforcement information adjustment unit 102 analyzes theplurality of ionospheric delay errors included in the reinforcementinformation on the order of centimeters that is selected in S1021 andcalculates, for each grid point, the coefficient value of thecoefficient included in the approximate expression used to calculate theapproximate value of the ionospheric delay error at each grid point.

The reinforcement information adjustment unit 102 further analyzes theplurality of tropospheric delay errors included in the reinforcementinformation on the order of centimeters that is selected in S1021 andcalculates, for each grid point, the coefficient value of thecoefficient included in the approximate expression used to calculate theapproximate value of the tropospheric delay error at each grid point.

The reinforcement information adjustment unit 102 then includes thecalculated coefficient value for each grid point into the reinforcementinformation on the order of centimeters that is selected in S1021, inplace of the ionospheric delay error at each grid point included in thereinforcement information on the order of centimeters that is selectedin S1021.

Moreover, the reinforcement information adjustment unit 102 includes thecalculated coefficient value for each grid point into the reinforcementinformation on the order of centimeters that is selected in S1021, inplace of the tropospheric delay error at each grid point included in thereinforcement information on the order of centimeters that is selectedin S1021.

A positioning device 600 is notified of the approximate expression foreach of an ionospheric delay error and the tropospheric delay error inadvance and applies, to the approximate expression, a coefficient valueincluded in reinforcement information on the order of decimeters 400received from a quasi-zenith satellite 200 or a wireless LAN network 800to be able to obtain the approximate value of each of the ionosphericdelay error and the tropospheric delay error at each grid point.

FIG. 9 is a diagram illustrating the operation of the reinforcementinformation adjustment unit 102 according to the present embodiment.

Each circle (o) in FIG. 9 indicates the error value (the ionosphericdelay error and the tropospheric delay error) at each grid point.

The positioning device 600 uses an approximate expression: (x,y)=ax²+by²+cx+dy+exy+f to be able to calculate the approximate value forthe error value at each grid point.

In the approximate expression, x denotes a latitude of the position ofthe grid point, y denotes a longitude of the position of the grid point,each of a, b, c, d, and e denotes the coefficient value calculated foreach grid by the reinforcement information adjustment unit 102, and fdenotes a constant.

Note that while a second-order polynomial is illustrated as an exampleof the approximate expression, the approximate expression is not limitedto a second-order expression.

The reinforcement information adjustment unit 102 analyzes the errorvalue for each grid point and calculates the value of each of thecoefficients a, b, c, d, and e in the approximate expression by a leastsquares method, for example.

The reinforcement information adjustment unit 102 then includes thevalue of each of the coefficients a, b, c, d, and e for each grid pointinto the reinforcement information on the order of centimeters that isselected in S1021, in place of the ionospheric delay error at each gridpoint included in the reinforcement information on the order ofcentimeters that is selected in S1021.

Moreover, the reinforcement information adjustment unit 102 includes thevalue of each of the coefficients a, b, c, d, and e for each grid pointinto the reinforcement information on the order of centimeters that isselected in S1021, in place of the tropospheric delay error at each gridpoint included in the reinforcement information on the order ofcentimeters that is selected in S1021.

While the positioning device 600 can calculate an estimated value ofeach of the ionospheric delay error and the tropospheric delay error foreach grid point by the approximate expression, there is an error asillustrated in FIG. 9 between the estimated value and each of actualionospheric delay error and tropospheric delay error.

The error is illustrated for only several grid points by reason ofdrawing in FIG. 9, but a difference between a graph of the approximateexpression and each circle is the error.

The reinforcement information adjustment unit 102 notifies of a decreasein reliability caused by using the approximate expression in the form ofintegrity information to be described later.

Next, in S1023 of FIG. 5, the reinforcement information adjustment unit102 reduces a bit count for each error value included in thereinforcement information on the order of centimeters after theprocessing in S1022.

The processing in S1023 is performed as illustrated in the firstembodiment.

Note that the reinforcement information adjustment unit 102 does notreduce a bit count of the coefficient value (the value of each of thecoefficients a, b, c, d, and e) included in the reinforcementinformation on the order of centimeters in S1022.

Through S1021 to S1023 described above, the amount of information in thereinforcement information on the order of centimeters is reduced to bethe reinforcement information on the order of decimeters.

The conversion into the reinforcement information on the order ofdecimeters by the method according to the present embodiment can alsoreduce the data volume to approximately one eighth compared to thereinforcement information on the order of centimeters.

Moreover, the reinforcement information adjustment unit 102 uses thereduced bit count and the approximate expression for the geographicinterval error value to be able to calculate reliability of thereinforcement information when the amount of information therein isreduced, on the basis of reliability of the reinforcement informationobtained from the reinforcement information on the order of centimeters.

The reinforcement information adjustment unit 102 can find thereliability of the reinforcement information on the order of decimetersby obtaining a root sum square (RSS) of the reliability of thereinforcement information on the order of centimeters, the decrease inthe reliability caused by the bit reduction, and the decrease in thereliability caused by using the approximate expression.

That is, the reinforcement information adjustment unit 102 calculates aroot sum square RSS of each error illustrated in FIG. 9 and calculates aroot sum square RSS of an error corresponding to the bit count reducedas illustrated in FIG. 8 to find the reliability of the reinforcementinformation on the order of decimeters.

The reinforcement information adjustment unit 102 then includes thereliability as the integrity information into the reinforcementinformation.

The reinforcement information adjustment unit 102 thus generates theintegrity information notifying of the decrease in reliability of thepositioning accuracy caused by the geographic interval error valueadjustment processing and the bit count adjustment processing andincludes the integrity information being generated into thereinforcement information on the order of decimeters.

A reinforcement information output unit 103 transmits the reinforcementinformation including the integrity information.

The integrity information allows a user who uses the reinforcementinformation on the order of decimeters to find reliability of ameasurement result from the reinforcement information in real time andis an essential piece of information in controlling a moving body.

***Description of Effect***

According to the present embodiment as well, the reinforcementinformation on the order of centimeters is converted to thereinforcement information on the order of decimeters to be able tocompress the data volume of the reinforcement information down toapproximately one eighth and allow a communication bandwidth to be usedeffectively.

Moreover, a smart phone, a mobile phone, a tablet terminal, a carnavigation system or the like can realize positioning with relativelyhigh accuracy on the order of decimeters even without a circuit or thelike for an L6 frequency.

Note that while there has been described in the first and secondembodiments that the processing of generating the reinforcementinformation on the order of decimeters is performed in the order of theupdate cycle adjustment processing S1021, the geographic interval errorvalue adjustment processing S1022 and the bit count adjustmentprocessing S1023 as illustrated in FIG. 5, the processing need not beperformed in this order but may be performed in a different order suchthat, for example, the update cycle adjustment processing S1021 isperformed after the geographic interval error value adjustmentprocessing S1022, followed by the bit adjustment processing S1023.

Third Embodiment

A positioning device 600 illustrated in FIG. 1 will be described indetail in the present embodiment.

Note that while there will be described an example in the presentembodiment that the positioning device 600 receives reinforcementinformation on the order of decimeters 400 and uses the reinforcementinformation on the order of decimeters 400 to perform satellitepositioning, the reinforcement information on the order of decimeters400 may be replaced by reinforcement information on the order ofcentimeters when the reinforcement information on the order ofcentimeters can be received to thus allow the positioning device toperform satellite positioning by using the reinforcement information onthe order of centimeters.

***Description of Configuration***

FIG. 10 illustrates a configuration example of the positioning device600 according to the present embodiment.

Moreover, FIG. 11 illustrates a brief description of each componentillustrated in FIG. 10, and FIG. 12 illustrates a brief description ofintermediate data.

An approximate position/satellite position calculation unit 601 receivesobserved data 501 and a broadcast ephemeris 502 from a GPS satellite 300and calculates an approximate position of a positioning point and aposition of each GPS satellite 300.

An approximate position 751 and a satellite position 752 are calculationresults of the approximate position/satellite position calculation unit601.

The approximate position 751 is a position of the positioning point thatis calculated by independent positioning and accurate on the order ofmeters.

The satellite position 752 is a position of each GPS satellite 300 fromwhich the positioning device 600 receives the observed data.

A correction data generation unit 602 receives the reinforcementinformation on the order of decimeters 400 from a quasi-zenith satellite200 as well as acquires the approximate position 751 and the satelliteposition 752 to calculate correction data 753 from the reinforcementinformation on the order of decimeters 400, the approximate position 751and the satellite position 752.

The correction data 753 indicates an error expected to be included inthe observed data 501 that is received at the positioning point fromeach GPS satellite 300.

An observed data screening unit 603 eliminates the observed data 501that is expected to be degraded in quality.

More specifically, the observed data screening unit 603 selects theobserved data 501 to be used in positioning calculation from among theplurality of pieces of observed data 501 on the basis of an angle ofelevation of the GPS satellite 300 being a positioning satellite fromwhich the observed data 501 is transmitted as well as received signalstrength of the observed data 501.

The observed data screening unit 603 for example has a threshold tablein which a plurality of ranges of the angle of elevation is indicatedand, for each range of the angle of elevation, a threshold of thereceived signal strength is defined.

The observed data screening unit 603 then refers to the threshold tableand selects a piece of observed data 501 when the received signalstrength of the observed data 501 is higher than or equal to a thresholdof the received signal strength defined in association with a range ofthe angle of elevation corresponding to the angle of elevation of theGPS satellite 300 from which the observed data is transmitted.

An observed data error correction unit 604 performs double differencecalculation to output double difference data 754 of the observed data.

The double difference data 754 indicates a value obtained by subtractingobserved data of a master satellite (observed data already corrected byusing the correction data 753) from observed data of a slave satellite(observed data already corrected by using the correction data 753).

A time extrapolation calculation unit 605 performs time extrapolationcalculation to estimate a state quantity X (t) of a current epoch from astate quantity X{circumflex over ( )}(t−Δt) of a previous epoch.

More specifically, the time extrapolation calculation unit 605 estimatesthe state quantity X (t) by using process noise adjusted by a processnoise adjustment unit 611 to be described later.

Note that notation in which “{circumflex over ( )}” lies directly above“X” in FIG. 10 is identical in meaning to the notation in which“{circumflex over ( )}” lies at the upper right of “X” (“X{circumflexover ( )}”).

Moreover, “{circumflex over ( )}” indicates a state quantity after beingupdated by an observation update calculation unit 608 to be described.

Note that the state quantity X (t) corresponds to the position and speedof the positioning device 600.

A geometric distance calculation unit 606 calculates a geometricdistance 755 from the GPS satellite 300 to the positioning point on thebasis of the satellite position 752.

A residual calculation unit 607 calculates a double difference residual756 from the double difference data 754 and the geometric distance 755.

The observation update calculation unit 608 updates the state quantity X(t) such that the state quantity X (t) has the smallest estimated error.

More specifically, the observation update calculation unit 608 updatesthe state quantity X (t) by using observation noise calculated by anobservation noise calculation unit 612 to be described later.

The state quantity X (t) after being updated by the observation updatecalculation unit 608 is denoted as a state quantity X{circumflex over( )} (t).

Note that a range enclosed with a dashed line in FIG. 10 is called apositioning calculation unit 609.

The positioning calculation unit 609 performs positioning calculation byusing the process noise adjusted by the process noise adjustment unit611 and the observation noise calculated by the observation noisecalculation unit 612.

A carrier smoothing processing unit 610 performs carrier smoothing onthe observed data 501 (a pseudorange and a carrier phase).

The process noise adjustment unit 611 adjusts the process noise used inthe positioning calculation by the positioning calculation unit 609(more specifically the time extrapolation calculation unit 605)according to the type of a moving body in which the positioning device600 is arranged.

The process noise adjustment unit 611 selects process noise smaller inthe altitude direction than a default value when the moving body inwhich the positioning device 600 is arranged is any of a vehicle, atrain and a ship, for example.

The observation noise calculation unit 612 uses integrity informationincluded in the reinforcement information to calculate the observationnoise used in the positioning calculation.

The integrity information is a piece of information presenting“certainty” of a positioning signal and is used at the time ofdetermining whether a positioning result can be used safely.

***Description of Operation***

In the present embodiment, there will be described the operation ofmainly the observed data screening unit 603, the time extrapolationcalculation unit 605, the observation update calculation unit 608, theprocess noise adjustment unit 611 and the observation noise calculationunit 612.

The observed data screening unit 603 selects the observed data 501 to besubjected to the processing by the observed data error correction unit604 and beyond, from among the pieces of the observed data 501 on whichthe carrier smoothing is already performed by the carrier smoothingprocessing unit 610.

The observed data screening unit 603 selects the observed data 501 to besubjected to the processing by the observed data error correction unit604 and beyond from among the plurality of pieces of the observed data501 on the basis of the angle of elevation of the GPS satellite 300 fromwhich the observed data 501 is transmitted as well as the receivedsignal strength of the observed data 501.

A positioning device has conventionally performed screening on observeddata used in positioning calculation on the basis of received signalstrength, where there has been uniformly applied a common threshold ofthe received signal strength regardless of the angle of elevationbetween the GPS satellite 300 and the positioning device.

There is a correlation between the angle of elevation of a satellite andthe received signal strength where, in general, the received signalstrength of the observed data increases as the angle of elevation of thesatellite increases.

When the received signal strength of observed data from a certain GPSsatellite 300 largely falls below the received signal strength fromanother GPS satellite 300 when the another GPS satellite 300 is at anequal angle of elevation, for example, it is presumed that quality ofthe observed data from the GPS satellite 300 is not very good even whenthe received signal strength of the GPS satellite 300 exceeds theuniform threshold.

Therefore, in the present embodiment, the observed data screening unit603 considers the correlation between the angle of elevation between thepositioning device 600 and the GPS satellite 300 and the received signalstrength of the observed data to select the observed data 501 to be usedin the positioning calculation.

The observed data screening unit 603 holds a threshold table illustratedin FIG. 13, for example.

In the threshold table of FIG. 13, a plurality of ranges of the angle ofelevation is indicated and, for each range of the angle of elevation, athreshold of the received signal strength is defined.

That is, in FIG. 13, as the ranges of the angle of elevation, ranges of10 to 20 degrees and 20 to 30 degrees are described, for example.

Note that in FIG. 13, the range of 10 to 20 degrees means 10.1 to 20.0degrees while the range of 20 to 30 degrees means 20.1 to 30.0 degrees.

The threshold table in FIG. 13 is generated by analyzing the correlationbetween the angle of elevation of the satellite and the received signalstrength of the observed data for a plurality of the GPS satellites 300.

The observed data screening unit 603 calculates the angle of elevationof the GPS satellite 300 from which the observed data 501 istransmitted, on the basis of the satellite position 752 calculated bythe approximate position/satellite position calculation unit 601.

The observed data screening unit 603 then refers to the threshold tablein FIG. 13 and selects the observed data 501 with the received signalstrength higher than or equal to a threshold of the received signalstrength defined in association with a range of the angle of elevationcorresponding to the calculated angle of elevation of the satellite,from among the plurality of pieces of the observed data 501 on which thecarrier smoothing is already performed.

The observed data screening unit 603 outputs only the selected observeddata 501 to the observed data error correction unit 604.

In order for the positioning calculation unit 609 to perform positioningcalculation, the observed data screening unit 603 needs to select fouror more of the observed data 501.

Next, there will be described a Kalman filter realizing the timeextrapolation calculation unit 605 and the observation updatecalculation unit 608.

FIG. 14 illustrates a processing flow of the Kalman filter.

FIG. 15 illustrates a description of a variable used in the processingof the Kalman filter.

The time extrapolation calculation unit 605 performs time extrapolationcalculation of the Kalman filter illustrated in FIG. 14.

Moreover, the observation update calculation unit 608 performsobservation update calculation of the Kalman filter illustrated in FIG.14.

The time extrapolation calculation and the observation updatecalculation form a single loop, the loop formed by the timeextrapolation calculation and the observation update calculation isexecuted repeatedly.

The Kalman filter estimates a state quantity such that a diagonalelement of an error variance (error variance matrixP_(ij)=E<x_(i)x_(j)>, where E<a> is a variance of “a”) of the estimatedstate quantity (state quantity X) is the smallest in each loop beingrepeated.

Processing performed in the Kalman filter will be described in dueorder.

In the time extrapolation calculation, from a state quantity(x{circumflex over ( )} (−)) and an error covariance matrix(P{circumflex over ( )} (−)) of a previous time, a state quantity (x(+)) and an error covariance matrix (P (+)) of a following time areestimated based on a transition matrix 4 determined according to adynamic model being adopted.

At this time, process noise Q that is an error expected between thedynamic model and an actual phenomenon is added to the error covariancematrix (P{circumflex over ( )} (−)).

The process noise Q is also determined according to the dynamic modeland design being adopted.

From the estimated state quantity (x (+)), an amount y⁻ equivalent to anobservation amount(y⁻ represents that “−” lies directly above “y”; thesame applies hereinafter) is obtained, the amount y⁻ being estimated byan observation model (y⁻=f (x)) expressing a relationship between thestate quantity and the observation amount.

In the observation update calculation, a residual (dz=y−y⁻) being adifference between an actual observation amount and the estimatedobservation amount is obtained and converted into a difference in thestate quantity (dx=K·dz) by using Kalman gain K expressed in anexpression in FIG. 14, whereby the state quantity is updated.

An observation matrix used in the observation update calculationexpresses the observation model and is obtained by the followingexpression.dz=H·dx(dz=y−y=f({circumflex over (x)})−f(x)=∇_(x)f·dx=H·dx)  [Expression 1]

Moreover, R included in the denominator of the expression of the Kalmangain K represents observation noise expected to be included in theobservation amount.

The process noise adjustment unit 611 adjusts the process noise providedto the time extrapolation calculation unit 605.

FIG. 16 illustrates default process noise and process noise obtainedafter being adjusted by the process noise adjustment unit 611.

Default process noise Q₃ has an X component (east-west direction), a Ycomponent (north-south direction) and a Z component (altitude direction)that are equal to one another with no anisotropy as illustrated in (a)of FIG. 16.

However, a vehicle, train or ship shifts in the altitude direction in agentle manner.

It is thus desired to set the process noise in the altitude directionsmaller than a default value when the vehicle, train or ship is themoving body in which the positioning device 600 is arranged.

Accordingly, in the present embodiment, the process noise adjustmentunit 611 selects f_(⊥) (0<f_(⊥)<<1) as the value of the process noise inthe altitude direction when the moving body is any of the vehicle, trainand ship (when the positioning device 600 is mounted in any of thevehicle, train and ship).

The process noise adjustment unit 611 then outputs process noise Q_(⊥)including f_(⊥) to the time extrapolation calculation unit 605, whichuses Q_(⊥) to perform the time extrapolation calculation illustrated inFIG. 14.

On the other hand, when the moving body in which the positioning device600 is arranged is a user (human), namely when the user carrying thepositioning device 600 is on the move on foot (when the positioningdevice 600 is not mounted in the vehicle, train or ship), the processnoise adjustment unit 611 outputs the default process noise Q₃ to thetime extrapolation calculation unit 605, which uses Q₃ to perform thetime extrapolation calculation illustrated in FIG. 14.

Moreover, when the moving body in which the positioning device 600 isarranged is an airplane, the process noise adjustment unit 611 outputsthe default process noise Q₃ to the time extrapolation calculation unit605, which uses Q₃ to perform the time extrapolation calculationillustrated in FIG. 14.

Note that the type of the moving body in which the positioning device600 is arranged is input to the positioning device 600 by the user, forexample, the type being the vehicle, train or ship, the user (human), orthe airplane.

Moreover, in FIG. 16, T_(ecef) ^(enu) is a matrix converting an ecefcoordinate system into an enu coordinate system.

Furthermore, each of Q₃ and Q_(⊥) is a matrix (process noise) in the enucoordinate system, and f_(⊥) is the value of the process noise in thealtitude direction when the moving body is any of the vehicle, train andship.

The observation noise calculation unit 612 calculates the observationnoise provided to the observation update calculation unit 608.

FIG. 17 illustrates conventional observation noise and the observationnoise calculated by the observation noise calculation unit 612.

The smaller the angle of elevation, the higher the possibility that asatellite signal is affected by an obstacle such as a building ormountain and the longer the distance for which the signal passes throughthe atmosphere and ionosphere causing a signal delay, so that theobservation noise of the satellite signal with the small angle ofelevation is conventionally large as illustrated in (a) of FIG. 17.

Low weighting is set to the observed data from a satellite having alarge value of the observation noise in the observation updatecalculation performed by the observation update calculation unit 608and, as a result, the data is reflected in a measurement result with asmall ratio.

The reinforcement information includes the integrity information.

In the integrity information, a high value is set to observed data froma satellite that is considered low in quality, whereas a low value isset to observed data from a satellite that is considered high inquality.

As described above, the observed data from the satellite with the smallangle of elevation is likely to be low in quality so that the observeddata from the satellite having the small angle of elevation andconsidered low in quality is desirably reflected in the positioningresult with a small ratio.

The observation noise calculation unit 612 according to the presentembodiment uses the integrity information in calculating the observationnoise to set the observation noise more properly.

More specifically, as illustrated in (b) of FIG. 17, the observationnoise calculation unit 612 reflects the value of the integrityinformation of a target GPS satellite in a formula of the observationnoise.

The observation noise calculation unit 612 outputs observation noise Rbeing a matrix of observation noise σ_(i) calculated by the formulaillustrated in (b) of FIG. 17 to the observation update calculation unit608, which uses the observation noise R to perform the observationupdate calculation illustrated in FIG. 14.

Note that in FIG. 17, i denotes a satellite number, σ_(i) denotes theobservation noise of a satellite i, and σ_(pr) denotes a designconstant.

Moreover, n denotes the number of satellites captured by the positioningdevice 600, and el_(i) denotes the angle of elevation of the satellitei.

Furthermore, denotes the integrity information of the satellite i.

The observation noise calculation unit 612 calculates the angle ofelevation of the satellite i on the basis of the satellite position 752calculated by the approximate position/satellite position calculationunit 601.

***Description of Effect***

Therefore, according to the present embodiment, the observed datascreening unit 603 selects the observed data used in the positioningcalculation while considering the angle of elevation of the satellite,whereby the observed data with good quality can be selected moreaccurately.

Moreover, according to the present embodiment, the process noiseadjustment unit 611 selects the process noise according to the type ofthe moving body, whereby the positioning accuracy can be improved byusing the process noise appropriate for the type of the moving body.

Furthermore, according to the present embodiment, the observation noisecalculation unit 612 uses the integrity information to calculate theobservation noise, whereby the positioning accuracy can be improved byincreasing the weighting on the observed data with high quality anddecreasing the weighting on the observed data with low quality.

These effects can then compensate for a decrease in the positioningaccuracy caused by the use of the reinforcement information on the orderof decimeters.

Fourth Embodiment

Another embodiment of a positioning device 600 will be described in thepresent embodiment.

***Description of configuration***

In the present embodiment as well, an example of the configuration ofthe positioning device 600 is as illustrated in FIG. 10.

However, in the present embodiment, when n (n≥5) pieces of observed datais selected on the basis of an angle of elevation of a satellite andreceived signal strength, an observed data screening unit 603 repeats anoperation of selecting m (m≥4 and m<n) pieces of observed data fromamong the n pieces of observed data. The observed data screening unit603 then generates k (k≥4 and k≤n) data sets, each of which is a dataset formed of the m pieces of observed data and has a differentcombination of the m pieces of observed data.

Moreover, in the present embodiment, an observation update calculationunit 608 of a positioning calculation unit 609 performs observationupdate calculation on the m pieces of observed data making up the dataset for each data set, and selects any data set from among the k datasets on the basis of a variance of a residual (double differenceresidual) before the observation update calculation of each data set anda variance of a residual (double difference residual) after theobservation update calculation of each data set.

More specifically, the observation update calculation unit 608 extractsa data set having the smallest variance of the residual after theobservation update calculation, and compares the variance of theresidual after the observation update calculation of the extracted dataset with a variance of a residual after update calculation of a data sethaving the second smallest variance of a residual after the observationupdate calculation.

When there is a significant difference between the variances, theobservation update calculation unit 608 determines whether or not avariance of a residual before the observation update calculation of theextracted data set is equal to or smaller than a threshold, and selectsthe extracted data set when the variance of the residual before theobservation update calculation of the extracted data set is equal to orsmaller than the threshold.

The observation update calculation unit 608 then handles the residual(double difference residual) in the extracted data set being selected asa state quantity X{circumflex over ( )} (t).

An operation of each of a process noise adjustment unit 611 and anobservation noise calculation unit 612 is the same as that illustratedin the third embodiment.

Moreover, in the third embodiment, an approximate position/satelliteposition calculation unit 601, a correction data generation unit 602, anobserved data error correction unit 604, a time extrapolationcalculation unit 605, a geometric distance calculation unit 606 and aresidual calculation unit 607 perform processing on the four or morepieces of observed data selected by the observed data screening unit 603whereas, in the present embodiment, the k data sets each formed of the mpieces of observed data is subjected to the processing.

However, except for the k data sets being subjected to the processing,an operation of each of the approximate position/satellite positioncalculation unit 601, the correction data generation unit 602, theobserved data error correction unit 604, the time extrapolationcalculation unit 605, the geometric distance calculation unit 606 andthe residual calculation unit 607 is the same as that illustrated in thethird embodiment.

That is, each of the approximate position/satellite position calculationunit 601, the correction data generation unit 602, the observed dataerror correction unit 604, the time extrapolation calculation unit 605,the geometric distance calculation unit 606 and the residual calculationunit 607 performs processing identical to that of the third embodimenton each data set.

***Description of Operation***

Next, an example of the operation of the positioning device 600according to the present embodiment will be described with reference toFIG. 18.

Since the operation of each of the observed data screening unit 603 andthe observation update calculation unit 608 of the present embodiment isdifferent from that of the third embodiment, there will be described anexample of the operation of mainly the observed data screening unit 603and the observation update calculation unit 608.

FIG. 18 illustrates an example where n=6, m=5, and k=6.

That is, FIG. 18 illustrates an example where the observed datascreening unit 603 selects six pieces of observed data from six GPSsatellites 300 on the basis of the angle of elevation of the satelliteand the received signal strength.

The observed data screening unit 603 generates a data set by selectingfive pieces of observed data from among the six pieces of observed data.

Here, the data set generated first is referred to as a data set #1.

In the example of FIG. 18, the data set #1 is formed of observed datafrom satellite 1, observed data from satellite 2, observed data fromsatellite 3, observed data from satellite 4, and observed data fromsatellite 5.

The observed data screening unit 603 outputs the generated data set #1to the observed data error correction unit 604.

The observed data error correction unit 604 performs double differencecalculation on the data set #1 as with the third embodiment andgenerates double difference data 754.

Moreover, the residual calculation unit 607 calculates a doubledifference residual 756 as with the third embodiment on the basis of thedouble difference data 754 generated from the data set #1 and ageometric distance 755.

The observation update calculation unit 608 performs the observationupdate calculation on the double difference residual 756 for the dataset #1.

The observation update calculation unit 608 further calculates avariance of the double difference residual 756 before the observationupdate calculation for the data set #1 and a variance of the doubledifference residual 756 after the observation update calculation for thedata set #1.

The processing performed up to this point corresponds to a first roundof loop.

Next, as processing performed in a second round of loop, the observeddata screening unit 603 generates a new data set by selecting fivepieces of observed data with a combination different from that of thedata set #1, from among the six pieces of observed data.

Here, the data set generated in the second round of loop is referred toas a data set #2.

In the example of FIG. 18, the data set #2 is formed of the observeddata from satellite 1, the observed data from satellite 2, the observeddata from satellite 3, the observed data from satellite 4, and observeddata from satellite 6.

The processing identical to that performed on the data set #1 isperformed on the data set #2. The observation update calculation unit608 calculates a variance of the double difference residual 756 beforethe observation update calculation for the data set #2 and a variance ofthe double difference residual 756 after the observation updatecalculation for the data set #2.

The processing performed up to this point corresponds to the secondround of loop.

Likewise, processing from a third round of loop to a sixth round of loopis performed from then on such that the observed data screening unit 603generates data sets #3 to #6 while the observation update calculationunit 608 calculates a variance of the double difference residual 756before the observation update calculation and a variance of the doubledifference residual 756 after the observation update calculation withrespect to each of the data sets #3 to #6.

Although the data sets #5 and #6 are omitted from FIG. 18 due to arestriction on drawing space, the data set #5 is formed of the observeddata from satellite 1, the observed data from satellite 3, the observeddata from satellite 4, the observed data from satellite 5, and theobserved data from satellite 6 while the data set #6 is formed of theobserved data from satellite 2, the observed data from satellite 3, theobserved data from satellite 4, the observed data from satellite 5, andthe observed data from satellite 6.

Moreover, in FIG. 18, a residual before observation update means adouble difference residual before the observation update calculation isperformed by the observation update calculation unit 608 while aresidual after observation update means a double difference residualafter the observation update calculation is performed by the observationupdate calculation unit 608.

Furthermore, in each of the residual before observation update and theresidual after observation update, a variance of a residual in loop 1corresponds to the variance of the residual in the data set #1.

The same applies to loop 2 and onward.

Once the processing on the sixth round of loop is completed with thevariance of the residual in each of loop 1 to loop 6 obtained for bothbefore and after the observation update, the observation updatecalculation unit 608 extracts a data set with the smallest varianceafter the observation update and a data set with the second smallestvariance.

Here, it is assumed that the variance of the data set #2 is the smallestand that the variance of the data set #3 is the second smallest.

The observation update calculation unit 608 determines whether or notthere is a significant difference between the variance of the data set#2 and the variance of the data set #3.

There may be prepared, for example, a threshold for the difference inthe variance (a difference threshold) so that the observation updatecalculation unit 608 determines there is the significant difference whenthe difference between the variance of the data set #2 and the varianceof the data set #3 exceeds the difference threshold.

When there is the significant difference between the variance of thedata set #2 and the variance of the data set #3, the observation updatecalculation unit 608 determines whether or not the variance before theobservation update of the data set #2 is small enough.

There may be prepared, for example, a threshold for the variance beforethe observation update (a variance threshold before observation update),so that the observation update calculation unit 608 determines thevariance before the observation update is small enough when the variancebefore the observation update of the data set #2 is smaller than orequal to the variance threshold before observation update.

When the variance before the observation update is small enough, theobservation update calculation unit 608 selects the data set #2 andhandles the double difference residual 756 after the observation updateof the data set #2 as the state quantity X{circumflex over ( )} (t) inFIG. 10.

***Description of Effect***

Therefore, according to the present embodiment, there can be obtainedthe combination of the observed data with which a more accuratepositioning result can be obtained.

Note that while the operation of each of the process noise adjustmentunit 611 and the observation noise calculation unit 612 is the same asthat of the third embodiment, the operation of each of the process noiseadjustment unit 611 and the observation noise calculation unit 612 neednot be the same as that of the third embodiment.

That is, the process noise adjustment unit 611 may be adapted to outputdefault process noise Q₃ illustrated in (a) of FIG. 16 to the timeextrapolation calculation unit 605 regardless of the type of a movingbody in which the positioning device 600 is arranged.

Moreover, the observation noise calculation unit 612 may be adapted tocalculate observation noise σ_(i) according to the expressionillustrated in (a) of FIG. 17 without using integrity information.

Furthermore, while the observed data screening unit 603 described aboveselects the n pieces of observed data by using the threshold of thereceived signal strength for each angle of elevation of a satellite aswith the third embodiment, the n pieces of observed data may be selectedby using a uniform threshold for the received signal strength notinvolving the angle of elevation of a satellite.

Moreover, while there has been described in the third and fourthembodiments the example of operation of the positioning device 600 thatreceives the reinforcement information on the order of decimeters 400, apositioning device receiving reinforcement information on the order ofcentimeters may be adapted to perform the same operation.

That is, the positioning device receiving the reinforcement informationon the order of centimeters may select observed data to be used inpositioning calculation from among a plurality of pieces of observeddata on the basis of the angle of elevation of a satellite and thereceived signal strength of the observed data.

The integrity information included in the reinforcement information onthe order of centimeters may also be used to calculate the observationnoise.

The positioning device receiving the reinforcement information on theorder of centimeters may also be adapted to adjust the process noiseaccording to the type of the moving body.

Moreover, the positioning device receiving the reinforcement informationon the order of centimeters may be adapted to generate k data sets fromthe n pieces of observed data and select any data set from among the kdata sets on the basis of a variance of a residual before theobservation update calculation of each data set and a variance of aresidual after the observation update calculation of each data set.

Furthermore, while there has been described in the third and fourthembodiments the example where the positioning device 600 receives thereinforcement information on the order of decimeters 400 from thequasi-zenith satellite 200, the reinforcement information on the orderof decimeters 400 may be received from a satellite other than thequasi-zenith satellite 200 or from the wireless LAN network 800providing a wireless LAN environment.

Specifically, where the positioning device 600 receives thereinforcement information on the order of decimeters 400 from asatellite other than the quasi-zenith satellite 200, the positioningdevice 600 may include a receiver used to receive a signal from thesatellite and input, to the correction data generation unit 602, thereinforcement information on the order of decimeters 400 received by thereceiver.

Alternatively, where the positioning device 600 receives thereinforcement information on the order of decimeters 400 from thewireless LAN network 800, the positioning device 600 may include awireless LAN receiver and input, to the correction data generation unit602, the reinforcement information on the order of decimeters 400received by the wireless LAN receiver.

Lastly, an example of a hardware configuration of each of theinformation processing device 100 and the positioning device 600according to the first to fourth embodiments will be described withreference to FIG. 19.

Each of the information processing device 100 and the positioning device600 is a computer that can implement each component in each of theinformation processing device 100 and the positioning device 600 by aprogram.

Each of the information processing device 100 and the positioning device600 has the hardware configuration in which an arithmetic unit 901, anexternal storage 902, a main storage 903, a communication unit 904 andan input/output unit 905 are connected to a bus.

The arithmetic unit 901 is a CPU (Central Processing Unit) executing theprogram.

The external storage 902 is a ROM (Read Only Memory), a flash memoryand/or a hard disk device, for example.

The main storage 903 is a RAM (Random Access Memory).

In the positioning device 600, the communication unit 904 receives theobserved data and the broadcast ephemeris from the GPS satellite andreceives the reinforcement information from the quasi-zenith satelliteor the wireless LAN network.

Moreover, the communication unit 904 in the positioning device 600includes an AD (analog-digital) conversion function.

The input/output unit 905 is a touch panel display, for example.

The program usually stored in the external storage 902 is sequentiallyread into the arithmetic unit 901 and executed while loaded to the mainstorage 903.

The program is a program implementing the function that is described as“ . . . unit” in FIGS. 3 and 10.

Moreover, the external storage 902 stores an operating system (OS), atleast a part of which is loaded to the main storage 903 so that thearithmetic unit 901 executes the program implementing the function ofthe “ . . . unit” illustrated in FIGS. 3 and 10 while executing the OS.

Furthermore, the main storage 903 stores as a file a piece ofinformation, data, a signal value and a variable value representing theresult of the processing described as “correction of . . . ”,“generation of . . . ”, “creation of . . . ”, “computation of . . . ”,“calculation of . . . ”, “adjustment of . . . ”, “determination of . . .”, “evaluation of . . . ”, “update of . . . ”, “estimation of . . . ”,“extraction of . . . ”, “selection of . . . ”, “reception of . . . ” andthe like in the first to fourth embodiments.

Note that the configuration in FIG. 19 merely illustrates an example ofthe hardware configuration of each of the information processing device100 and the positioning device 600, which may thus have the hardwareconfiguration that is not necessarily the configuration illustrated inFIG. 19 but another configuration.

While the embodiments of the present invention have been described, twoor more of those embodiments may be combined and implemented.

Alternatively, one of those embodiments may be partially implemented.

Yet alternatively, two or more of those embodiments may be partiallycombined and implemented.

Note that the present invention is not to be limited by thoseembodiments but can be modified in various manners as needed.

REFERENCE SIGNS LIST

100: information processing device, 101: reinforcement informationgeneration unit, 102: reinforcement information adjustment unit, 103:reinforcement information output unit, 200: quasi-zenith satellite, 300:GPS satellite, 400: reinforcement information on the order ofdecimeters, 500: positioning signal, 600: positioning device, 601:approximate position/satellite position calculation unit, 602:correction data generation unit, 603: observed data screening unit, 604:observed data error correction unit, 605: time extrapolation calculationunit, 606: geometric distance calculation unit, 607: residualcalculation unit, 608: observation update calculation unit, 609:positioning calculation unit, 610: carrier smoothing processing unit,611: process noise adjustment unit, 612: observation noise calculationunit, 700: transmitter, 800: wireless LAN network, 1021: update cycleadjustment processing, 1022: geographic interval error value adjustmentprocessing, and 1023: bit count adjustment processing

The invention claimed is:
 1. An information processing device used tocorrect a satellite positioning error, comprising: circuitry including aprocessor coupled to memory and configured to: generate reinforcementinformation that is updated in a predetermined cycle, includes aplurality of error values, and is used to correct the satellitepositioning error; reduce an amount of information in the reinforcementinformation by degrading the reinforcement information on an order ofcentimeters to reinforcement information on an order of decimeters; andoutput, to a wireless network, the reinforcement information after beingreduced in the amount of information, wherein the circuitry reduces theamount of information in the reinforcement information by combining:update cycle adjustment processing to set an update cycle of thereinforcement information to be an integer multiple being twice or moreof the predetermined update cycle; geographic interval error valueadjustment processing to reduce the number of geographic interval errorvalues by selecting from among a plurality of the geographic intervalerror values each of which is an error at every predetermined geographicinterval in a plurality of grid points, out of the plurality of errorvalues, a geographic interval error value at every geographic intervalthat is an integer multiple being twice or more of the predeterminedgeographic interval in each of a latitude direction and a longitudedirection; and bit count adjustment processing to reduce a bit count ofthe error value, for each error value relevant to a carrier wave,starting from a least significant bit, such that a bit count afterreduction is smaller than a bit count before the reduction.
 2. Theinformation processing device according to claim 1, wherein thecircuitry is further configured to: process, as the update cycleadjustment processing, to set the update cycle of the reinforcementinformation to be twice the predetermined update cycle; process, as thegeographic interval error value adjustment processing, to reduce thenumber of the geographic interval error values by selecting thegeographic interval error value at every geographic interval that istriple the predetermined geographic interval in each of the latitudedirection and the longitude direction from among the plurality of thegeographic interval error values; and process, as the bit countadjustment processing, to reduce the bit count, for each error valuerelevant to the carrier wave, starting from the least significant bit,such that the bit count after the reduction is equal to any bit countbetween 60% and 80% of the bit count before the reduction.
 3. Theinformation processing device according to claim 1, wherein thecircuitry to perform the geographic interval error value adjustmentprocessing, is configured to: process to reduce the number ofionospheric delay error values by selecting an ionospheric delay errorvalue at every geographic interval that is triple the predeterminedgeographic interval in each of the latitude direction and the longitudedirection from among a plurality of the ionospheric delay error values;and process to reduce the number of tropospheric delay error values byselecting a tropospheric delay error value at every geographic intervalthat is triple the predetermined geographic interval in each of thelatitude direction and the longitude direction from among a plurality oftropospheric delay error values.
 4. An information processing deviceused to correct a satellite positioning error, comprising: circuitryincluding a processor coupled to a memory and configured to: generatereinforcement information that is updated in a predetermined cycle,includes a plurality of error values, and is used to correct thesatellite positioning error; reduce an amount of information in thereinforcement information by degrading the reinforcement information onan order of centimeters to reinforcement information on an order ofdecimeters; and output, to a wireless network, the reinforcementinformation after being reduced in the amount of information, whereinthe circuitry reduces the amount of information in the reinforcementinformation by combining: update cycle adjustment processing to set anupdate cycle of the reinforcement information to be an integer multiplebeing twice or more of the predetermined update cycle; geographicinterval error value adjustment processing to analyze a plurality of thegeographic interval error values each of which is an error at everypredetermined geographic interval in a plurality of grid points, out ofthe plurality of error values, calculate, for each geographic interval,a coefficient value of a coefficient included in an approximateexpression used to calculate an approximate value of the geographicinterval error value, and include the coefficient value for eachgeographic interval in the reinforcement information in place of theplurality of the geographic interval error values; and bit countadjustment processing to reduce a bit count of the error value, for eacherror value relevant to a carrier wave, starting from a leastsignificant bit, such that a bit count after reduction is smaller than abit count before the reduction.
 5. The information processing deviceaccording to claim 4, wherein the circuitry is further configured to:process, as the update cycle adjustment processing, to set the updatecycle of the reinforcement information to be twice the predeterminedupdate cycle; and process, as the bit count adjustment processing, toreduce the bit count, for each error value relevant to the carrier wave,starting from the least significant bit such that the bit count afterthe reduction is equal to any bit count between 60% and 80% of the bitcount before the reduction.
 6. The information processing deviceaccording to claim 4, wherein the circuitry to perform the geographicinterval error value adjustment processing is configured to: process toanalyze a plurality of ionospheric delay error values, calculate, foreach geographic interval, a coefficient value of a coefficient includedin an approximate expression used to calculate an approximate value ofthe ionospheric delay error value, and include the coefficient value foreach geographic interval in the reinforcement information in place ofthe plurality of the ionospheric delay error values; and process toanalyze a plurality of tropospheric delay error values, calculate, foreach geographic interval, a coefficient value of a coefficient includedin an approximate expression used to calculate an approximate value ofthe tropospheric delay error value, and include the coefficient valuefor each geographic interval in the reinforcement information in placeof the plurality of the tropospheric delay error values.
 7. Theinformation processing device according to claim 1, wherein thecircuitry generates integrity information notifying of a decrease inreliability of positioning accuracy caused by the geographic intervalerror value adjustment processing and the bit count adjustmentprocessing, and includes the generated integrity information intoreinforcement information after being reduced in the amount ofinformation, and the circuitry outputs, to the wireless network, thereinforcement information after being reduced in the amount ofinformation which includes the integrity information.
 8. The informationprocessing device according to claim 4, wherein the circuitry generatesintegrity information notifying of a decrease in reliability ofpositioning accuracy caused by the geographic interval error valueadjustment processing and the bit count adjustment processing, andincludes the generated integrity information into reinforcementinformation after being reduced in the amount of information, and thecircuitry outputs, to the wireless network, the reinforcementinformation after being reduced in the amount of information whichincludes the integrity information.